Komisarek played two seasons at the University of Michigan, piling up 46 points and 145 penalty minutes in 80 games. He helped the Wolverines to a 55-24-10 mark, a CCHA title and two trips to the NCAA Frozen Four.[1] One of his teammates was fellow Long Islander Eric Nystrom, who was drafted by the Calgary Flames. Komisarek was also named a First Team Division I All-American by the American Hockey Coaches Association in 2002.

After two seasons with the University of Michigan, Komisarek was selected seventh overall in the 2001 NHL Entry Draft by the Montreal Canadiens. He played his first NHL game in the 2002–03 season with the Canadiens. He re-signed with the Canadiens in 2007 for a 2-year contract for 3.5 million dollars, along with his friend Christopher Higgins, who is also from Long Island.

Komisarek scored his first NHL goal, vs the Washington Capitals on March 20, 2006, where he was named the first star of the game.[2] His willingness to stand up for his teammates and his hard-hitting style made him a fan favourite in the Bell Centre.

During the 2007-08 season, Komisarek led the league with 227 blocked shots and finished second in hits with 266 having played only 75 games.

On January 5, 2009 played in the 57th NHL All-Star Game and was named a starter as voted by the fans alongside his defense partner Andrei Markov. [4]

In July 2009, Komisarek signed a 5-year contract with the Toronto Maple Leafs, averaging $4.5 million per season. On January 2, 2010, Komisarek injured his shoulder in a game against the Calgary Flames, and on February 3, 2010, it was revealed he would require season-ending surgery. This also meant Komisarek would miss the 2010 Winter Olympics, as he was chosen to represent Team USA.[5]

On March 20, 2013 Komisarek was placed on waivers by the Toronto Maple Leafs. On March 21, 2013, he cleared waivers and with his permission he was assigned to the Maple Leafs American Hockey League affiliate, the Toronto Marlies for the remainder of the 2012–13 season. With one year left on his contract with the Maple Leafs, Komisarek was released as a free agent after his contract was used in a compliance buy-out on July 2, 2013.[6]

On July 5, 2013, he signed as a free agent to a one-year deal worth $700,000 with the Carolina Hurricanes.[7]

In September 2014, Komisarek was signed to a Professional Tryout Contract by the New Jersey Devils, but was released from it shortly after.

Komisarek is of Polish descent. His father, Roman Komisarek, was 24 when he moved to the U.S., where he eventually opened an auto-body repair shop on Long Island.[8] Roman Komisarek left his wife Kathy behind in Poland until he could earn enough to afford an apartment and support her. Speaking of his parents' move to the U.S., Komisarek stated that, "At that time, my parents knew they wanted to start a family and give me and my sister a better opportunity. [...](My father) moved to Brooklyn, found a job and didn't know the language at all. He just had the clothes on his back. Now, we have a nice home on Long Island, and my parents provided everything we ever needed. I always carried that with me. I always wanted to make them proud." [9] Komisarek also has a sister named Joanne, who is two years younger than he is. His sister is a graduate of Boston College.[8] He also speaks Polish.

Komisarek's mother, Kathy, was diagnosed with pancreatic cancer in January 2005 and died in November 2005. She was 51.[10]

In 2014, Komisarek announced that he would be resuming studies at the University of Michigan through the athletic department's Degree Completion Program. [11] On January 9, 2015 Michigan Wolverines head coach Red Berenson announced that Komisarek would join the coaching staff as an undergraduate student assistant.[12]